Fix RTCAudioSession crash in removeDelegate.

webrtc/modules/audio_device/ios/objc/RTCAudioSessionTest.mm

 /*
  *  Copyright 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 28 matching lines @@
 }
 
 - (void)audioSessionShouldConfigure:(RTCAudioSession *)session {
 }
 
 - (void)audioSessionShouldUnconfigure:(RTCAudioSession *)session {
 }
 
 @end
 
+// A delegate that adds itself to the audio session on init and removes itself
+// in its dealloc.
+@interface RTCTestRemoveOnDeallocDelegate : RTCAudioSessionTestDelegate
+@end
+
+@implementation RTCTestRemoveOnDeallocDelegate
+
+- (instancetype)init {
+  if (self = [super init]) {
+    RTCAudioSession *session = [RTCAudioSession sharedInstance];
+    [session addDelegate:self];
+  }
+  return self;
+}
+
+- (void)dealloc {
+  RTCAudioSession *session = [RTCAudioSession sharedInstance];
+  [session removeDelegate:self];
+}
+
+@end
+
 
 @interface RTCAudioSessionTest : NSObject
 
 - (void)testLockForConfiguration;
 
 @end
 
 @implementation RTCAudioSessionTest
 
 - (void)testLockForConfiguration {
@@ skipping 76 matching lines @@
   // The previously created delegate should've de-alloced, leaving a nil ptr.
   EXPECT_FALSE(session.delegates[0]);
   RTCAudioSessionTestDelegate *delegate =
       [[RTCAudioSessionTestDelegate alloc] init];
   [session addDelegate:delegate];
   // On adding a new delegate, nil ptrs should've been cleared.
   EXPECT_EQ(1u, session.delegates.size());
   EXPECT_TRUE(session.delegates[0]);
 }
 
+// Tests that we don't crash when removing delegates in dealloc.
+// Added as a regression test.
+- (void)testRemoveDelegateOnDealloc {
+  @autoreleasepool {
+    RTCTestRemoveOnDeallocDelegate *delegate =
+        [[RTCTestRemoveOnDeallocDelegate alloc] init];
+    EXPECT_TRUE(delegate);
+  }
+  RTCAudioSession *session = [RTCAudioSession sharedInstance];
+  EXPECT_EQ(0u, session.delegates.size());
+}
+
 @end
 
 namespace webrtc {
 
 class AudioSessionTest : public ::testing::Test {
  protected:
   void TearDown() {
     RTCAudioSession *session = [RTCAudioSession sharedInstance];
     for (id<RTCAudioSessionDelegate> delegate : session.delegates) {
       [session removeDelegate:delegate];
@@ skipping 14 matching lines @@
 TEST_F(AudioSessionTest, PushDelegate) {
   RTCAudioSessionTest *test = [[RTCAudioSessionTest alloc] init];
   [test testPushDelegate];
 }
 
 TEST_F(AudioSessionTest, ZeroingWeakDelegate) {
   RTCAudioSessionTest *test = [[RTCAudioSessionTest alloc] init];
   [test testZeroingWeakDelegate];
 }
 
+TEST_F(AudioSessionTest, RemoveDelegateOnDealloc) {
+  RTCAudioSessionTest *test = [[RTCAudioSessionTest alloc] init];
+  [test testRemoveDelegateOnDealloc];
+}
+
 }  // namespace webrtc